Authenticity of SCJP/OCPJP 6 vouchers

Are there any means to authenticate the SCJP/OCPJP voucher? Am from a place where anything can be duplicated and manipulated. Tried to search about it in the net but found nothing helpful.

I had contacted an institute and they were eager to sell the vouchers and also promised discounts on bulk purchase. Thus, I wanted to make sure about the authenticity of the voucher that I was gonna buy.

As per my knowledge, there's no 'method' to authenticate the vouchers, however, it can be ensured by following:

1) When you make a purchase, you'll get two different mails. One mail containing actual voucher (i.e. a zip file in which there will be a pdf etc. containing voucher). This zip attachment would be password protected. Second mail will contain password to it. Make sure that both mails are sent by authentic email address. Cross check the addersses with the vendor.

2) Before purchasing a voucher, check out what is expiry date and then decide if you want to buy a voucher right now or at the time of exam. If date of your preference is not a rush hour (which is generally last month or last two weeks of expiry period), then you can simply book the appointment before purchasing the voucher, and on the day of exam, simply walk in with cash/card and make a purchase. In this case, you will get a mail, which you'll open after the exam (but once you've given the exam, who cares about voucher number? ). However, please note that this facility can be availed only if vendor is having both facilites : Oracle vouchers and Pearson VUE center. Also, please note that if your appointment is during the rush hour, then the vendor might not book an appointment for you without purchasing the voucher.

3) Buy voucher from reputed institutes. I've bought all my vouchers either from SEED Infotech and NIIT. I never had any bad experience. Those(or other reputed) institutes also give you a receipt of voucher. Also, don't forget to provide your email address accurately and cross check it before the operator hit the purchase button(so that only you will get the mail).